A problem exists in the field of architectural opening covers, shade systems, with regard to the raising and lowering of the cover and associated elements such as lift cords and bottom bars, as are known in the art. Prior art solutions include motor driven systems connected to outside power sources. These systems are powerful enough to simply muscle a cover up and down no matter what the weight of the system and despite the high torque requirements to be overcome. These systems are usually bulky, noisy and expensive. Further, despite the advantages the un-counterbalanced weight of the shade system eventually will wear out these systems and lead to expensive replacement options.
For each particular shade system, a certain amount of torque must be applied to raise and lower a shade. Thus, each shade system has a particular “shade system torque profile”. With powered systems, the prior art solution, again, is simply to apply more than enough power to overcome the torque requirements. Shades and blinds such as cellular shades and Venetian blinds always have approximately the same suspended weight whether the blind is in the open or closed position. This differentiates their counterbalancing requirements from roll shades which lose weight as the shade is reeled onto the storage roll. In both cases the drive shaft or storage roll must rotate to adjust the shade over the opening and the effects on the counterbalances are different. Counterbalanced systems are known in the art that attempt to offset at least partially the heavy weight and torque requirements of a shade system so that quieter, less expensive battery powered systems are possible. Most of these systems known to the Applicants involve complicated arrangements of springs, gears and transmission systems.
U.S. Pat. No. 6,283,192, to Toti discloses a spring drive system for window covers which includes a so-called flat spring drive and the combination whose elements are selected from a group which includes (1) a band transmission which provides varying ratio power transfer as the cover is opened and closed; (2) a gear system selected from various gear sets which provide frictional holding force and fixed power transfer ratios; and (3) a gear transmission which provides fixed ratio power transfer as the cover is opened or closed. The combination permits the spring drive force at the cover to be tailored to the weight and/or compression characteristics of the window cover such as a horizontal slat or pleated or box blind as the cover is opened and closed.
U.S. Pat. No. 6,536,503, to Anderson et al. discloses a modular blind transport system for a window blind application. The complete system purportedly may be assembled form a relatively small number of individual modules to obtain working systems for a very wide range of applications, including especially a category of counterbalanced blinds wherein a relatively small external input force may be used to raise or lower the blind, and/or to open or close the blind.
U.S. Pat. No. 6,648,050, to Toti shows a spring drive system useful for window covers which comprises one or more coil spring drives or flat spring drives and the combination whose elements are selected from one or more of a group which includes (1) a band or cord transmission which provides varying ratio power transfer as the cover is opened and closed; (2) gear means comprising various gear sets which provide frictional holding force and fixed power transfer ratios; (3) a gear transmission which provides fixed ratio power transfer as the cover is opened or closed; (4) crank mechanisms; (5) brake mechanisms; and (6) recoiler mechanisms. The combination of all these elements is said to permit the spring drive force to be tailored to the weight and/or compression characteristics of an associated window cover such as a horizontal slat or pleated or box blind as the cover is opened and closed.
U.S. Pat. No. 6,957,683 to Toti discloses a spring drive system said to be useful for window covers which comprises one or more coil spring drives or flat spring drives and the combination whose elements are selected from one or more of a group which includes (1) a band or cord transmission which provides varying ratio power transfer as the cover is opened and closed; (2) gear means comprising various gear sets which provide frictional holding force and fixed power transfer ratios; (3) a gear transmission which provides fixed ratio power transfer as the cover is opened or closed; (4) crank mechanisms; (5) brake mechanisms; and (6) recoiler mechanisms. The combination of all of these elements is said to permit the spring drive force to be tailored to the weight and/or compression characteristics of an associated window cover such as a horizontal slat or pleated or box blind as the cover is opened and closed.
U.S. Pat. No. 6,983,783 to Carmen et al. discloses a motorized shade control system that includes electronic drive units (EDUs) having programmable control units directing a motor to move an associated shade in response to command signals directed to the control units from wall-mounted keypad controllers or from alternate devices or control systems connected to a contact closure interface (CCI). Each of the EDUs, keypad controllers and CCIs of the system is connected to a common communication bus. The system provides for initiation of soft addressing of the system components from any keypad controller, CCI or EDU. The system also provides for setting of EDU limit positions and assignment of EDUs to keypad controllers from the keypad controllers or CCIs. The system may also include infrared receivers for receiving infrared command signals from an infrared transmitter.
U.S. Pat. No. 7,185,691 to Toti discloses a reversible pull cord mechanism adapted for rotating a shaft in one direction when the pull cord is pulled in a first direction and rotating the shaft in the opposite direction when the pull cord is pulled in a second direction.
In sum, each of the prior art systems attempts to overcome by brute electrical mechanical force the shade torque profile created by the weight of the hanging shade and connected elements of a particular shade system or to partially compensate for, to counterbalance, the weight by means of complicated spring, gear and transmission systems. Further, prior art spring counterbalance systems generally overcompensate to ensure complete retrieval of an extended shade and thus require weight to be added to the bottom bar of a shade to ensure the shade fully extends and to prevent the shade from retracting inadvertently. This extra weight wears on the system, causes batteries to drain more quickly and is an added expense. Importantly, none of the prior art systems known to Applicants enables a user to construct a counterbalance system that approximates the torque profile of any particular shade system without undue overcompensation and that is easy to add to and delete from as circumstances dictate.
Thus, there is a need in the art for a counterbalance for shade systems that is applicable to all sizes of shade systems that is capable of providing a counterbalance that matches or nearly matches the torque requirements of each particular shade system and that does not require intricate gears or transmissions.
It therefore is an object of this invention to provide a spring counterbalance for a shade system that includes the combination of at least two spring systems that create a counterbalance torque profile that matches or approximates the torque profile of a subject shade system. It is a further object of the invention to provide a spring counterbalance apparatus and method that is easy to assemble, install and maintain.